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Raised blood platelet levels 'strong predictor' of cancer

Having a high blood platelet count is a strong predictor of cancer and should be urgently investigated to save lives, according to a large-scale study led by the University of Exeter Medical School and supported by PenCLAHRC.

Around two per cent of people over 40 – up to half a million people in the UK – have a raised blood platelet count, known as thrombocytosis.

Now, a study of 40,000 patient records has found that more than 11% of men and 6% of women over the age of 40 with thrombocytosis, went on to be diagnosed with cancer within a year. This rose to 18% of men and 10% of women if a second raised platelet count was recorded within six months.

In the general population, around 1% of people develop cancer in any one year. In the cohort analysed, around 4% of men and 2% of women who had been sent for a blood test by their GP, developed cancer.

People with lung and colorectal cancer were more commonly diagnosed with thrombocytosis. One-third of patients with thrombocytosis and lung or colorectal cancer had no other symptoms that would indicate to their GP that they had cancer.

Lead author Dr Bailey said:

“We know that early diagnosis is absolutely key in whether people survive cancer. Our research suggests that substantial numbers of people could have their cancer diagnosed up to three months earlier if thrombocytosis prompted investigation for cancer. This time could make a vital difference in achieving earlier diagnosis.”

The research was carried out using data from the UK Clinical Practice Research Datalink, which includes anonymised data from around 8% of UK general practices. The researchers analysed the records of 30,000 patients with thrombocytosis and 8,000 with normal blood platelet counts.

The study has revealed the first new indicator of cancer to have been robustly identified in 30 years. The researchers calculate that if only a conservative estimate of 5% of patients with cancer have thrombocytosis before a cancer diagnosis, one third of them could be diagnosed at least three months earlier if this risk marker was identified. This would equate to 5,500 earlier diagnoses annually.

“The UK lags well behind other developed countries on early cancer diagnosis. In 2014, 163,000 people died of cancer in this country. Our findings on thrombocytosis show a strong association with cancer, particularly in men – far stronger than that of a breast lump for breast cancer in women. It is now crucial that we roll out cancer investigation of thrombocytosis. It could save hundreds of lives each year.”